1. Field of Endeavor
The present invention relates to the field of steam turbines, and to a steam turbine with heating steam extraction.
2. Brief Description of the Related Art
Heating heat decoupling from condensing turbines is a current measure for district heat generation. With this, in most cases the heating steam is decoupled from the tappings of the low pressure turbine, in order to achieve an energetically optimum solution at a low temperature level.
With large heating output and, as a result of it, large steam extraction volumes, the tapping slots and branches of the low pressure turbine have a limiting effect so that special medium pressure turbine sections for heating steam extraction are necessary. Such a solution is already known from U.S. Pat. No. 4,628,693.
In steam turbines with very high electrical power output (for example >500 MW) and at the same time very high heating heat generation with low flow temperatures and return temperatures, the volumetric flows of steam which are to be decoupled are no longer controllable by the previous concepts. For modern steam turbine processes, high reheater pressures and reheater temperatures are also necessary, so that the expansion to the very low pressure level of the heaters which are arranged in the district heating circuit has to be distributed not in one but in two series-connected MP turbines.